The present invention relates to an image control display apparatus which can simply and effectively edit the stored image data into desired display formats.
For displaying a document prepared by a document writer or a word processing machine on a display screen, after the prepared document data is written into an image memory, the stored document data is read out and then seen as a document on the screen. A common practice is to store the image data in an image memory with a capacity for storing image data almost equal to that of the image data displayed on the full area of the display screen of the display unit. For changing the document currently being displayed, the image data in the image memory must be rewritten every time such a document is changed. Also when two different documents, for example, are simultaneously displayed, it is necessary that the image data of the corresponding documents be edited and written into a single image memory. As described above, the conventional apparatus must rewrite the contents of the image memory every time the display contents are changed. This procedural operation is troublesome.
A conceivable countermeasure taken for this problem is to store beforehand in a plurality of the image memories some different document data to be displayed. In this countermeasure, when the display on the screen is to be changed, all an operator has to do is to access the image memory which stores the document data to be displayed. Further, by simultaneously reading out two or more document data and editing them in a data processor, two or more documents can readily be displayed on the same display screen.
Such a countermeasure, of using a plurality of the image memories, however, suffers from an increase in hardware in the image display control apparatus. This results in a complicated construction of the image display control apparatus and the increased manufacturing cost. Because of these problems, the conventional apparatus is impractical.